ADR 0237, to-be 45 Phase 5: a change is judged against the mesh that runs before it merges

The operator approved Phase 5. Decides what the design left open: the build seat runs the
merge check, the facts live in the artifact store, the merge gate composes the mesh as it is
and with the change and judges only what the change adds, a replay lives where its incident
is, and the controller's tests run a bus of their own at the mesh's release. A core issue now
resolves only with a replay or a stated reason, checked by cycle.py.

00-META/checks/cycle.py

@@ -16,6 +16,11 @@ What is enforced:
           once `resolved`, `fixed-by:` says what fixed it (prose counts --
           "nothing, the capability existed" is an answer). And no two records share a
           number -- the number is how a record is cited.
+  replays a core issue -- one opened from 2026-10-07 whose `located-in:` names a core repository --
+          resolves only with `replay:` (the replay's id in mesh-lab's replays register) or
+          `replay-none:` (why no replay is possible): ADR 0237, to-be 45 §9. A replay is what
+          proves a fix fails before and passes after; without one, a fixed class comes back
+          through a different door (research 031: four such chains in one week).
   research a known `status:`; a `graduated` overview says what it `became:`, and every
           target it names exists.
   decisions every accepted record is REACHABLE from the cycle: cited by a design doc's
@@ -41,6 +46,16 @@ DESIGN_STATUSES = {"proposed", "designed", "in-progress", "implemented", "abando
 ISSUE_STATUSES = {"open", "diagnosing", "located", "resolved", "wontfix"}
 RESEARCH_STATUSES = {"active", "graduated", "abandoned"}
 
+# The core, as to-be 45 names it, by where its code lives: the controller, the node-engine, the node
+# tools and the console, the SDK's loops, and the catalogue's bus, forge (the announcer of merges) and
+# build agent. A `located-in:` entry naming any of these makes an issue a core issue.
+CORE = re.compile(r"\b(mesh-controller|mesh-host|mesh-tools|mesh-sdk|node-tools|"
+                  r"mesh-catalog\s+modules/(nats|gitea|build-agent))\b")
+
+# The day the rule began (ADR 0237): issues opened before it are not held to it.
+REPLAYS_FROM = "2026-10-07"
+REPLAY_ID = re.compile(r"^R\d+\b")
+
 
 def rel(path):
     return os.path.relpath(path, ROOT)
@@ -159,6 +174,16 @@ def main():
             bad(path, "status %s but located-in is empty" % status)
         if status == "resolved" and not listy(front, "fixed-by"):
             bad(path, "status %s but fixed-by says nothing" % status)
+        # A core issue resolves with its replay, or with why none is possible (ADR 0237).
+        replay = " ".join(listy(front, "replay"))
+        if replay and not REPLAY_ID.match(replay):
+            bad(path, "replay: %r names no replay -- an id from mesh-lab's replays register, R<issue>" % replay)
+        core = any(CORE.search(entry) for entry in listy(front, "located-in"))
+        opened = str(front.get("opened") or "")
+        if (status == "resolved" and core and opened >= REPLAYS_FROM and not replay
+                and not " ".join(listy(front, "replay-none")).strip()):
+            bad(path, "a core issue resolved with no replay: name it in `replay:` (mesh-lab replays "
+                      "register.go) or say in `replay-none:` why none is possible (ADR 0237)")
 
     # ---- research ----------------------------------------------------------------------
     for path in sorted(glob.glob(os.path.join(ROOT, "01-RESEARCH", "*", "00-overview.md"))):